Pokémon Change (ポケモンチェンジ, Pokémon Change) is Pokémon Trainer's down special move. It is one of only two moves that all three of the Trainer's Pokémon have in common (the other being their Final Smash, Triple Finish). It switches between his three Pokémon - Charizard, Squirtle, and Ivysaur. If Charizard is currently in use, it will switch to Squirtle. If Squirtle is in use, it will switch to Ivysaur. If Ivysaur is in use, it will switch to Charizard. Using this move too little will result in the Pokémon's stamina being drained. Only one Pokémon needs be knocked out to score against Pokémon Trainer.
If one Pokémon is KO'd, Pokémon Trainer will summon the next Pokémon in the rotation to the revival platform. Pokémon Change cannot be used again until the starting invincibility has worn off. Pokémon Change also cannot be used in midair.
While changing, there is a little time in which the Pokémon have invincibility frames. Thus the switching animation, which takes some time, can be used to "dodge" various attacks, most notably certain Final Smashes.
Notably, using Pokémon Change ends nearly all status effects on the Pokémon, both positive and negative. This includes super or mini size, Starman invincibility, metal form, Franklin Badges, Screw Attacks, etc. The exceptions to this rule are slowed-time, healing in progress, and Smash Ball readiness, all of which remain through the change. Any held item is immediately dropped.
Like Zelda's Transform, the next Pokémon to appear must be loaded from the disc before the switch can be completed. Pausing can shorten the in-game switch time (since the game loads during the pause), as can lag when online. If the switch time is artificially shortened as such, replays will temporarily freeze at the point the switch is made (since it must take the full time to load). Forcing the game to load the next character through an SD card via hacking will result in a near-instant switch time.
A technique known as "zero switching" can be performed on horizontally moving platforms, which allows a Pokémon to switch out while leaving the player free to react immediately after the next Pokémon is switched in. To perform the technique, the player must initiate Pokémon Change while standing on the edge of a platform that is moving out from under them (such as the right edge of the Smashville platform that is moving left). If done properly, the next Pokémon will appear in the air, leaving the player free to immediately input any aerial action. The zero switch also gives Squirtle and Ivysaur two midair jumps instead of one upon reappearance. Zero switching is commonly used competitively to avoid the high ending lag that results from switching normally (since the move cannot be started in midair, but this technique allows it to at least be ended in midair).
At the start of a match, each Pokémon has 100 points of stamina. When a Pokémon is in battle, its stamina drops by half a point every second. (This equates to 3 minutes and 20 seconds of stamina.) The Pokémon also loses half a point of stamina for every attack it attempts. Once a Pokémon's stamina drops to 40, its standing animation switches to signal fatigue. When the Pokémon's stamina reaches zero, its attacks drop in damage by a factor of 0.7x (with corresponding reduced knockback as a result). Pokémon regain 0.8 points of stamina per second when not being used (equating to 2 minutes and 5 seconds to fully "recharge"), and all Pokémon's stamina are increased by 1.3x when any one of them is KO'd.
In The Subspace Emissary, the stamina stat is removed, allowing exclusive usage of one Pokémon.
The concept of stamina is generally detrimental towards Pokémon Trainer's competitive usage. As a clear attempt at forcing players to utilize the group character's full array of options instead of sticking to one of the three Pokémon for an entire match, Pokémon Trainer mains are forced to learn three different characters just to stay on top of the game, let alone take control of it, and are penalized for using a single form for too long. This can also cause problems in terms of matchups, where for example one Pokémon may hard counter a certain opponent, but the player is unable to take advantage of this due to being forced to either switch or suffer a significant strength reduction, giving the opponent a large opening to strike back. This is in clear contrast to other transforming characters, such as the Transform mechanic for Zelda and Sheik, which has no such penalties.
While the phrase "Pokémon Change" itself is not an official term in the Pokémon universe, it describes the act of switching out a Pokémon mid-battle. It is a crucial tactic in the games, both in-game and competitively, and takes place before all other actions for that turn (with the sole exception of the move Pursuit, which is designed to counter switching). In the games, as switching takes up the user's turn, the benefits of switching in a Pokémon to face a target it is effective against must be weighed against the risks of being hit hard, setup on, or simply outpredicted by the opponent.
In the Pokémon games, switching out a Pokémon cures minor status effects and all temporary stat modifications, but major status effects and HP will remain unchanged. This can be compared and contrasted to Brawl, where a switched-out Pokémon retains damage, but regains stamina and has almost all status effects removed.
The concept of stamina as Brawl uses it does not exist in the Pokémon games. There is no mechanic that naturally makes a Pokémon less effective the longer it remains in play, unless one counts the fact that moves have limited uses and a single Pokémon used too long will eventually be unable to do anything. Even then however, these limited uses do not replenish while the Pokémon is switched out.